Sponge-like material soaks up sunlight, uses it to make steam

Published on September 9th, 2014 | By: Jessica McMathis

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[Image above] A new sponge-like material developed by MIT researchers soaks up the sun and uses it to make steam. The material incorporates two hydrophilic layers, one of carbon foam and one of exfoliated graphite, that draw water to the surface. Credit: MIT

It’s far from a polar vortex, but the summer of 2014 hasn’t been ideal for my usual warm-weather tan.

I’m a water baby, a sun worshipper, and a mindful sunscreen applier—but this central Ohio summer has lacked the regular sunshine I require to build a healthy glow.

Though I may not be soaking up the sun, a new material developed by scientists at MIT is—and it’s using that sunlight to make steam.

The disc-shaped, sponge-like structure is porous, insulating, and floats on water. Its two hydrophilic layers—one of ultra-absorbing flakes of graphite and one of insulating foam—draw water to the surface. The graphite acts as a hotspot, soaking up the sun’s energy and releasing it as steam. And, just as with my tan, more bright light means that much more steam.

MIT’s material isn’t the only one on the solar-powered, steam-generating block, but what helps it to stand out from the crowd is its better-than-average ability to use solar energy to make steam—85 percent of incident solar energy powers the water-to-steam conversion.

According to an MIT News report, their approach “generates steam at a solar intensity about 10 times that of a sunny day—the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.”

“This is a huge advantage in cost-reduction,” says Hadi Ghasemi in the story. Ghasemi is a post-doc in MIT’s mechanical engineering department and one of the authors of the Nature Communications paper detailing the work. “That’s exciting for us because we’ve come up with a new approach to solar steam generation.”

According to MIT, “the setup loses very little heat in the process and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.”

Also relatively low is the cost of the materials needed to make the structure.

“Steam is important for desalination, hygiene systems, and sterilization,” says Ghasemi. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”